The present invention relates generally to ultrasonic welding and more particularly to welding at least two layers of material together.
Ultrasonic welding of dissimilar materials is known. In today""s manufacturing society, lightweight composite materials are desirable and often substituted in an attempt to build lighter and stronger products. Such manufacturing often requires the joining of several layers of lightweight materials formed of various combinations and alloys, such as aluminum and magnesium. In a typical automotive application, the two aluminum layers sandwich a magnesium layer between them. These layers must be connected to one another or, put succinctly, welded together to form a single unitary component.
As known with ultrasonic welding, the strength and degree of weld penetration decreases the further the distance from the sonotrode tip. Accordingly, when welding multiple layers of material the weld lessens in strength at the subsequent or lower interfaces; i.e., the weld at the interfaces between the lower layers is not as strong as the weld at the interface between the top and immediately adjacent layer.
Accordingly, the present invention is an ultrasonic welding apparatus and method for joining layers of materials. The method includes the steps of clamping multiple layers of materials between a sonotrode and an anvil of an ultrasonic welding apparatus. Once clamped, the ultrasonic welding apparatus, specifically the sonotrode, forms a weld between at least the top and intermediate layer of the multi-layer member, wherein the first or top layer is adjacent the sonotrode. Then, rotating either the multi-layer member or the ultrasonic welding apparatus wherein the bottom layer of the multi-layer member is now positioned adjacent the sonotrode. Once the sonotrode is positioned adjacent the bottom or lower layer, the layers are once again clamped and a weld is formed between at least the bottom and intermediate layer.
In an additional embodiment, the intermediate layer may include a plurality of layers. In some instances, additional layers are placed on and overlay the outer layers of the multi-layer member. These layers are also ultrasonically welded thereto. This process results in an ultrasonically welded multi-layer composite member.
The ultrasonic welding assembly includes an ultrasonic welding gun having a C-shape frame including a base portion and a head portion joined together to form the C-shape frame. The C-shape frame further defining a throat area between the base portion and head portion. An ultrasonic welding device, including a sonotrode is secured to the head portion. Secured to the base portion is an anvil. The ultrasonic welding assembly further includes a robot connected to the ultrasonic welding gun. The robot operates to position and rotate the ultrasonic welding gun to perform the welding operation.
In a further embodiment, an additional ultrasonic welding device replaces the anvil of the ultrasonic welding gun positioned on the base portion. Accordingly, the ultrasonic welding gun welds from either side of the multi-layer member without removing and rotating either the multi-layer member or the ultrasonic welding gun.
In an additional embodiment, the anvil and sonotrode assembly are positioned on separate supports or frames. Accordingly, both the anvil and sonotrode move independently to a specific location to perform a welding operation rather than moving the multi-layer member.